At present, the production of a headrest by casting in situ a mixture of polyurethane consists in the first instance in producing by sewing or cementing a cover, constituting an external envelope of the headrest, in cloth, PVC or leather, placing this cover in a conforming mold, casting within this cover a foaming mixture of polyurethane which, after expansion, entirely fills said cover, and, finally, demolding, after polymerization of said foaming mixture, the covered headrest thus obtained.
Nevertheless, before casting the foaming mixture, it is indispensable to place within the cover a metallic insert generally constituted by a metallic rod in the shape of a horseshoe embedded in the polyurethane foam, but the ends of whose legs emerge from the base of the headrest. These two ends slide within the upper end of the seat back. There is thus obtained a headrest adjustable in height by sliding, but not inclinable forwardly and rearwardly relative to the back.
To obtain an inclinable headrest, it is necessary to provide each of the two legs of the insert with an articulation. These two articulations are generally located for aesthetic reasons and for efficiency, entirely within the interior of the headrest, but immediately adjacent the point of emergence of the two legs of the insert to the outside of the headrest.
Moreover, to permit the swinging of the articulated legs in the headrest at the level of the articulations, it was absolutely necessary on the one hand to provide suitable slots in the external covering of the headrest and, on the other hand, to prevent any penetration of polyurethane foam into the space in which said articulated legs swing.
To this end, it is at present indispensable to provide about these articulations protective frames, ordinarily of injected plastic material, on the one hand, to prevent, during casting in situ of the polyurethane foam, and more particularly, at the end of expansion of said foaming mixture, any loss of foam into the slots preliminarily provided in the external covering and, on the other hand, to delimit during casting in situ and during the expansion phase of the foaming mixture, the future spaces for swinging of said articulated legs.
The major drawback of these protective frames is their high cost, which of course increases the total sale price of the headrest.